Low-temperature Fischer-Tropsch synthesis was investigated in micro packed-bed reactors. Co/Re/-Al2O3 catalysts with different particle shapes and sizes (60 to 580m) were employed. Tubular reactor geometry with lengths of up to 1m was chosen. Pressure drop measurements in the absence of reaction and during reaction were carried out. For analysis of the experimental data a reactor model was developed, which was also used for the determination of liquid holdup. It could be observed that the liquid holdup is independent of conversion, reaction temperature, C5+ productivity, and reaction rate. For irregularly shaped catalyst particles, a liquid holdup in the range of 3% was observed.